This research is designed to obtain detailed information about the molecular structure of peptide hormones regulating growth and development, with emphasis on placental lactogen as a member of the growth hormone-prolactin family. A second primary objective is to characterize the relationships between these hormones and their receptor structures in order to elucidate the molecular bases for information transfer from hormone to target cell. A third primary objective is to understand the mechanisms by which this group of hormones regulates cell processes related to growth and development. To expand our knowledge of primary structure, essential for investigation of structure-function relationships, major effort is directed toward isolation, characterization, and sequence analysis of sub-primate placental lactogens. Additional studies will be carried out on the structure of pre-placental lactogen from the same sub-primate species. Data on primary structure will be utilized in the examination of evolutionary relationships among placental lactogens, prolactins and growth hormones of various species and with other hormonal peptides. To investigate structure-function relationships of lactogenic and growth hormones, use will be made of cell culture methodology, with emphasis on primary monolayer culture of several cell types, including mammary epithelium. This will facilitate a comparative study of the effects of native placental lactogen, and fragments derived from it by chemical and enzymatic modification, on biological activity.